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Overview: Koselugo is used for certain types of tumors in people who have a genetic condition called neurofibromatosis type 1 (NF1). Common side effects include nausea and vomiting, rash, and stomach pain. Tell your health care provider right away if you get diarrhea, a rash, swelling, vision changes, or shortness of breath. These could be signs of a serious side effect. Keep all appointments with your health care provider before, during, and after taking Koselugo. Koselugo is a capsule that is swallowed.

Uses

What is Koselugo used for?

Koselugo (selumetinib) is commonly used to treat certain types of tumors in some people who have a genetic condition called neurofibromatosis type 1 (NF1).

Koselugo may also be used for other conditions as determined by your health care provider.

How does Koselugo work (mechanism of action)?

Koselugo works by blocking certain proteins, called MEK1 and MEK2 (MEK1/2). MEK1/2 helps tell cells to grow. When MEK1/2 is too active, it can make tumor cells grow quickly. By blocking MEK1/2, Koselugo helps prevent tumor cells from growing.

How is Koselugo supplied (dosage forms)?

Brands and other names

  • Koselugo

Dosage forms and strengths

  • 10 mg and 25 mg oral capsules

How should I store Koselugo?

Koselugo should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place. Keep it in the original bottle, tightly closed. Protect from moisture. The bottle contains a desiccant packet to help keep the capsules dry, which should be left in the bottle. Do not throw the packet away. 

Side Effects

What are the most common side effects of Koselugo?

The most common side effects of Koselugo are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Nausea and vomiting
  • Rash (see below)
  • Stomach pain
  • Diarrhea (see below)
  • Dry skin
  • Tiredness
  • Muscle problems, such as muscle and bone pain (see below)
  • Fever
  • Acne-like rash
  • Mouth sores
  • Headache
  • Nail infection (paronychia)
  • Itching

There may be other side effects of Koselugo that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of Koselugo?

While less common, the most serious side effects of Koselugo are described below, along with what to do if they happen.

Severe Allergic Reactions. Koselugo may cause allergic reactions, which can be serious. Stop taking Koselugo and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives, which can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Heart Problems. Koselugo may cause your heart muscle to become enlarged, thickened, or stiffened and not work as well, also known as cardiomyopathy. Keep all appointments with your health care provider to check your heart before starting and while taking Koselugo. Tell your health care provider right away if you have any of the following symptoms.

  • Shortness of breath, coughing, wheezing, or trouble breathing
  • Swelling in your feet, ankles, legs, or hands
  • Unusual tiredness
  • Heartbeat that flutters or feels fast or pounding

Severe Eye Problems. Koselugo may cause severe eye problems, such as blocked blood vessels in your eye (retinal vein occlusion). These problems can lead to blindness. Keep all scheduled eye exams before starting and while taking Koselugo. Contact your health care provider right away if you have any of the following symptoms.

  • Flashes of light in your vision
  • “Floaters” or small flecks or threads in your vision
  • Eye redness, itchiness, or pain
  • Swollen or itchy eyelids
  • Feeling like you have something in your eye
  • Eye dryness, watering, or discharge
  • Vision changes, such as blurry vision, loss of vision, or sensitivity to light

Diarrhea. Diarrhea is common with Koselugo, and it can sometimes be severe. Koselugo may also increase your risk of serious gut problems, including inflamed intestines (colitis) or a gut tear (perforation). Call your health care provider right away if you have diarrhea. If you are given medicine to prevent or treat diarrhea, take it exactly as your health care provider tells you. You should also make sure to drink plenty of fluids if you have diarrhea. 

Rash or Skin Reactions. Koselugo can commonly cause a rash, and sometimes it can be severe. Koselugo may also cause other skin-related side effects, such as an acne-like rash, maculopapular rash, or eczema. It may also cause “hand-foot” syndrome, also called palmar-plantar erythrodysesthesia syndrome. Hand-foot syndrome can cause you to have numbness, tingling, or changes in feeling in the palms of your hands and soles of your feet. It may also cause redness, swelling, or pain in your hands and feet. Call your health care provider right away if you have any of these symptoms.

Muscle Problems. Koselugo can cause increased levels of creatine phosphokinase (CPK), which may be a sign of damage to your muscles. In some people, the muscle may break down (rhabdomyolysis), which can be serious and rarely lead to kidney damage and death. Attend all appointments with your health care provider to have your blood checked. Contact your health care provider right away if you have any muscle aches or pain, muscle weakness, spasms, or dark-colored urine (pee).

Warnings & Precautions

Who should not use Koselugo?

Allergies to Ingredients. People who are allergic to any of the following should not take Koselugo.

  • Koselugo
  • Selumetinib
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in Koselugo.

What should I know about Koselugo before using it?

Do not take Koselugo unless it has been prescribed to you by a health care provider. Take it as prescribed.

Do not share Koselugo with other people, even if they have the same condition as you. It may harm them.

Keep Koselugo out of the reach of children.

Do not crush, chew, cut, open, or dissolve Koselugo. The medicine should be swallowed whole with water. 

If you throw up (vomit) after taking your dose of Koselugo, do not take an extra dose. Take your next dose at the regularly scheduled time. 

Keep all appointments, including for blood tests and heart checks, before starting and while you are taking Koselugo. This helps your health care provider know if this medicine is safe for you.

What should I tell my health care provider before using Koselugo?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if Koselugo is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have or have had any of the following.

  • Heart problems
  • Eye problems
  • Liver problems
  • Bleeding problems

Other Medicines and Supplements. Koselugo may interact with other medicines and supplements. Before taking Koselugo, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. Koselugo may cause harm to a fetus. Your health care provider will likely make sure you are not pregnant before starting to take Koselugo. If you are able to get pregnant, you should use effective birth control while taking Koselugo and for one week after your last dose. If you are able to get a partner pregnant, you should use effective birth control while taking Koselugo and for one week after your last dose. Talk with your health care provider about your birth control options. Tell your health care provider right away if you are pregnant, think you might be pregnant, or plan to become pregnant.

Breastfeeding. It is not known if Koselugo passes into breast milk. You should not breastfeed while taking Koselugo and for one week after your last dose. Tell your health care provider if you are breastfeeding or plan to breastfeed.

How can I get more information about Koselugo?

For more information about Koselugo, you can visit the drugmaker’s website at www.koselugo.com or call them at 800-236-9933.

Interactions

Does Koselugo interact with foods or drinks?

Grapefruit interacts with Koselugo. It is important to avoid eating grapefruit or drinking grapefruit juice while taking Koselugo. This is because grapefruit can affect your body’s ability to break down Koselugo, which can lead to high levels of the medicine and an increased risk of side effects.

It is unknown if drinking alcohol will affect Koselugo.

Does Koselugo interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking Koselugo.

  • Vitamin E, which is a supplement that may be found in many OTC products, including some multivitamins
  • Aspirin, which is in many prescription and OTC products, including those for pain, swelling, and fever
  • A blood thinner, which is a medicine used to treat or prevent blood clots
  • An antiplatelet medicine, such as aspirin/dipyridamole, cilostazol, clopidogrel (Plavix), or ticagrelor (Brilinta), which is a medicine used to prevent blood clots
  • St. John’s wort, which is a supplement that may be used for depression
  • Fluconazole (Diflucan), itraconazole (Sporanox, Tolsura), ketoconazole, posaconazole (Noxafil), or voriconazole (Vfend), which are medicines used for fungal infections

Many other medicines may alter the blood levels of Koselugo. Tell your health care provider about all medicines that you take or have recently taken.

This may not be a complete list of medicines that can interact with Koselugo. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much Koselugo?

If you or someone else has used too much Koselugo, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of Koselugo?

If you miss a dose, take it as soon as you remember. If it is less than six hours until your next dose, skip the missed dose and only take the next dose at the usual time. Do not take double or extra doses.